Method of manufacturing primers



L. T. MEISTER 2,455,380

METHOD OF MANUFACTURING PRIIERS 2 Shaeta-Sheet 1 LEQTI MEiETEH,

7, 1948. L. 'r. MEISTER 2,455,380

IETH OD OF IANUFACTURING PRIIERS Filed 7, 1945 2 snets-sneet 2" ma 1 jwwm LEQTMEQETER,

Patented Dec. 7, 1948 UNlTED STATES PATENT OFFICE METHOD OF MANUFACTURING PBIMERS Leo T. Meister, Bradley Beach, N. J.

Application May 7, 1945, Serial No. 592,433

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to artillery ammunition primers and to a method or process of manufacturing them.

An object of the invention is the provision of an artillery ammunition primer in which the igniter charge contained within the igniter charge tube or body of the primer is effectively sealed therein against harmful influences of air, gases or liquids.

Another object of the invention is the provision of an artillery ammunition primer in which the interior liner for the igniter charge tube containing the flash or flame holes is formed of a fusible thin-walled metallic seamless tube closed at one end and all formed of an integral piece of metal, as for example by a drawing operation. Such an integral closed end tube or liner may be formed from a disk or slug of metal by drawing operations involving the use of a punch and die, more or less in the same manner as cartridge cases are drawn from disks or cups of brass. Closed end seamless tubes of the type referred to above resemble an elongated sewing thimble having cylindrical walls, and are referred to herein and in the appended claims as thimbles.

These thimbles may be made of any easily fusible suitable metal which is subject to plastic flow in drawing and which may be cemented or soldered within the igniter charge tube, as hereinafter more fully appears. These thimbles are advantageously formed of tin or lead, or alloys of tin or lead, for example, alloys of lead and tin consisting of 50% lead and 50% tin, and 60% lead and 40% tin. In the further description which follows, the thimbles are considered as being made of or drawn from an alloy of lead and tin consisting of 60% lead and 40% tin, it being understood, however, that the invention is not confined to the use of this particular metal or alloy, as will be understood by the person skilled in the art. Thimbles formed of alloys of lead and tin have proved to be very satisfactory in the practice of the invention.

A further object of the invention is the provision of a primer for artillery ammunition in which the thimble liner hereinbefore mentioned is connected at or near its open end with the interior wall of the igniting charge tube by means of an air-tight connection.

Still another object of the present invention is the provision of a method of manufacturing the artillery ammunition primer referred to above and described more in detail hereinafter.

Referring to the accompanying drawing in which the same numeral appearing in difierent views indicates the same part,

Figure 1 is an elevation of a primer manufactured according to the present invention;

Figure 2 is a longitudinal central section of the primer along the line 2-2 of Figure 1;

Figure 3 is an enlarged central longitudinal section of a part of a primer at the position where the thimble is joined, as by cementing or soldering, to the igniter charge tube;

Figure 4 is a cross section on the line 4-4 of Figure 1;

Figures 5 to 9, inclusive, illustrate the method or process of manufacturing the primers;

Figure 5 is a perspective view of one of the thimbles;

Figure 6 is a perspective view showing the open end of the thimble submerged in a soldering flux;

Figure 7 is a perspective view showing the thimble on an expanding mandrel which is illustrated in longitudinal section in Figure 9;

Figure 8 is a view similar to Figure '7 in which the igniter charge tube has been pushed over the thimble on the mandrel, whereby the thimble becomes positioned within the igniter charge tube;

Figure 9 is a longitudinal section of an expanding mandrel with the thimble and igniter charge tube thereon, the expanding mandrel being shown in expanded condition;

Figure 10 is a perspective view showing a high frequency induction heating coil around the igniter charge tube containing the thimble, for heating the tube at the areas adjacent the open end of the thimble.

Referring now in detail to the accompanying drawings, and in particular, to Figures 1 to 4, which illustrate the construction of the primer, the numeral 5 indicates an igniter charge tube and the numeral 6 indicates the head at the firing end of the tube 5. Head 6 contains the usual percussion elements which are not shown in the drawings, since these percussion elements are not a part of the present invention. Head 6 is attached to igniter charge tube 5 by a portion of the former engaging with screw threads 1 within igniter tube 5. The head 6 engages with the tube 5 tightly, and preferably tight enough that there is air-tight engagement or connection between the head 6 and the igniter charge tube 5. As shown, igniter charge tube 5 is provided with a screw threads.

number of vents or flame holes 8 for the passage of flame arising from the igniter charge when the primer is fired. The igniter charge tube 5 is advantageously made of brass.

A thin-walled lead-tin alloy thimble, as described and defined above, is located within the igniter charge tube 5. This thimble closely fits within the interior of the igniter charge tube 5 and covers all of the flame holes 8 thereof. The closed end of the thimble is adjacent the closed end ll of the igniter tube 5. The open end of thimble I is located adjacent the imperforate part of the igniter tube between the screw threads 1 and the openings nearest the said Thimble I0 is made slightly smaller in diameter than the interior diameter of igniter charge tube 5 so that it may be inserted easily within igniter charge tube 5, and into the position shown in Figure 2. The cylindrical wall portion and the closed end wall portion of the thimble iii are, respectively, pressed against the cylindrical interior wall and closed end of the igniter charge tube 5 in any suitable manner, so that the walls of the thimble abut against the interior walls of the igniter charge tube, particularly at the open end of the thimble. Prior to inserting the thimble l0 into the igniter tube 5 into the position shown in Fi ure 2, a soldering flux is applied around the thimble at the open end. This flux, which is preferably a non-acid flux, extends around the thimble for a short distance, for example a quarter to a half inch, from the open end of the thimble towards the' closed end. Thus, in manufacture, a soldering flux lies between the wall of the thimble near its open end and the interior imperforate portion of the igniter charge tube 5. The soldering flux may be rosin, which is applied to the open end of the thimble by dipping the open end, to the extent indicated above, in a body of rosin in the melted condition, or into a. body of a solution of rosin in a suitable solvent, for example, spirits of turpentine or alcohol. Preferably the rosin applied to the thimble should be allowed to solidify or dry (in the case of a solution of rosin) before the thimble i0 is inserted into the igniter charge tube 5.

Heat is now applied to the exterior of the igniter charge tube 5 and localized in the area of the tube near the open end of the thimble Ill. The heat applied should be of sufficient intensity to effect the soldering of the cylindrical wall portion of the thimble, near the open end thereof,.

to the interior wall of the igniter charge tube 5.

The soldering action extends completely around i the thimble at or near the open end thereof, whereby an air-tight or gas-tight connection is made between the walls of the thimble near its open end and the adjacent imperforate portions of the igniter charge tube 5. In Figure 3 of the drawing, showing, on enlarged scale, a portion of the igniter charge tube 5 near the open end of thimble In, the soldering between the thimble l0 and the igniter charge tube extends the distance indicated by the letter S. The cylindrical wall of the thimble melts during the heating for a length corresponding to the distance S, and owing to the fact that the thimble is made of a material which is a solder, it becomes soldered to the interior wall of the igniter charge tube 5 upon cooling after the described heating. The soldering between the igniter tube 5 and the thimble I0 is only effected near the open end of the thimble, so that the remainder of the walls of the thimble are unattached to, but pressed against, the interior walls of the igniter charge tube 5.

In loading the primer, a black powder charge or other igniter charge is inserted into the thimble l0 after it is soldered into position as above described and as shown in Figure 2. Thereupon the head 6 containing the percussion elements is screwed into tight engagement with screw threads I. The primer is now ready for use in connection with fixed, semi-fixed or separate loading ammunition. The striking of the percussion cap or element in the head 5 produces a flame which ignites the igniter charge of black powder, or other igniter charge, which has been placed within the fusible thimble III. The buming of the igniter charge produces flame which melts the fusible thimble and this flame passes to the exterior of the igniter charge tube 5 through the openings 5. The jets of flame issuing from the openings 8 ignite the explosive or propellant charge in connection with which th primer herein described is used. I

From the foregoing it will be apparent that the thimble Ill may be formed of any metal that is readily fusible by the heat or flame produced by the burning of the igniter charge and that can be soldered to the igniter charge tube 5. A feature of the embodiment of the invention hereinbefore described resides in the fact that the thimble I0 is formed or constructed of a lead-tin alloy which itself provides the solder for soldering the thimble l0. at its upper end to the igniter charge tube 5. In the event that thimble II is formed of a metal which does not function as a solder, the walls of the thimble near the open end are tinned with an appropriate solder and then a soldering flux applied to the so tinned portion before the thimble is placed within the igniter charge tube 5.

A further advantage in using thimbles formed wholly or in part of tin, or comprising tin as a component of the metal thereof, is that the products resulting from the destruction of the thimble by the burning of the igniter charge promotes or causes decoppering of the bore of cannon.

Reference is now made to Figures 5 to 9, inclusive, which illustrate the present preferred method of manufacturing the artillery ammunition primer described above. illustrated in perspective in Figure 5. Figure 6 illustrates the first step of method, which consists in dipping the open end of the thimble into a body of liquid or liquefied soldering flux 20 held within any suitable container 2| to which heat may be applied, if necessary, to maintain the flux at a suitable temperature or in molten condition. The open end of the thimble II is submerged in the flux for a distance of from onequarter to one-half inch, more or less. The flux is allowed to solidify or dry on the thimble before proceeding with the next step of the method.

Figure 7 illustrates the second step of the method in which the thimble I0 is placed upon or pushed over an expanding mandrel 22 held by a support 23. The construction of the expanding mandrel is illustrated in detail in Figure 9. As shown in Figure 9, the expanding mandrel comprises a rubber tube 25 closed at one end by a rubber plug 25 cemented to the interior of the tube 25 by a rubber cement. The opposite end of the rubber tube 25 is connected with the nipple 21 of the union 28 which connects the space within tube 25 with the compressed air line 29. The support 23 may be divided along the line 30 to facilitate assembly of the mandrel The thimble I5 is 22 therewith. The two parts of the support may be secured together in any suitable manner.

Figure 8 illustrates the third step of the method in which the igniter charge tube 5 has been placed over, or pushed over, the thimble III which is still on the expanding mandrel 22. The expanding mandrel is of sufiicient length to reach the closed end of the thimble I and to press this closed end against the closed end ll of the igniter charge tube 5. The mandrel is now expanded by causing compressed air to fiow from the line or tube 29 into the hollow interior of the mandrel. The rubber walls of the mandrel expand and press the cylindrical wall of the thimble against the interior cylindrical wall of the igniter charge tube 5. After the walls of the thimble have been pressed against the interior wall of the igniter charge tube by expansion of the mandrel, the compressed air is released from the mandrel, whereupon the mandrel contracts to its former unexpanded condition. After this contraction of the mandrel, the igniter charge tube 5 with the thimble therein is removed from the mandrel. The thimble I0 remains within the igniter charge tube 5, adhering to its interior walls when it is removed from the contracted mandrel.

Thimbles made of soft metals such as tin or lead, or alloys of them, are an important feature in the method of manufacture of the primer, in that thimbles of such materials can be stretched or enlarged by the expansion of the expanding mandrel 22, whereby a thimble slightly smaller than the interior of the igniter charge tube 5 before expansion of the expanding mandrel, is stretched or enlarged enough by the expansion of the mandrel to snugly fit against the interior wall of the igniter charge tube 5. This facilitates soldering, and insures effective soldering, in the next step of the method, because when the heat is applied in the next step, the Walls of the thimble near its open end are in such close relation with the interior wall of the igniter charge tube 5 that soldering takes place practically at the same instant that the open end of the thimble begins to melt. The solder from the melting end of the thimble immediately wets the adjacent interior walls of the igniter charge tube 5.

The fourth step of the method is illustrated in Figure 10. In this step, the fluxed end of the thimble I0 is soldered to the imperforate portion of the igniter charge tube 5. In order to effect soldering of the thimble to the igniter charge tube, the said tube is heated circumferentially in the vicinity of the open end of the thimble l0 which is in position in said tube. This heating may be accomplished by means of a high frequency induction heating coil 3 I' placed about the tube about at the position of the open end of the thimble. As soon as the wall of the thimble at or near its open end melt, the igniter charge tube 5 '6 is withdrawn from the coil 3| and allowed to cool.

I claim: 1. That method of manufacturing a primer comprising, positioning a thin-walled thimble of a lead-tin alloy soldering material having a soldering flux on its exterior, within a perforate metallic igniter charge tube having one end closed, expanding said thimble into snug fitting engagement with said tube, and heating said tube and thimble to bring at least the open end of said thimble and the adjacent portion of said tube to soldering temperature, whereby said thimble and tube are rigidly united.

2. That method of manufacturing a primer having a thin-walled imperforate thimble of a leadtin alloy soldering material secured Within a perforate flash tube having one end closed, said method comprising, coating the exterior of said thimble adjacent its open end with soldering flux, inserting said thimble into said tube with the closed ends of said tube and thimble adjacent, expanding said thimble into intimate contact with the inner walls of said tube, and heating the contacting flux-coated portion of said thimble and the contacting surface of said tube to soldering temperature, to thereby rigidly unite said tube and thimble.

3. That method of closing the flash holes of a primer tube with a thimble formed of a lead-tin alloy, said tube having one end closed, comprising, applying a soldering flux to a portion of the exterior of said thimble adjacent its open end, inserting said thimble into said tube with the closed end thereof adjacent the closed end of said tube,

expanding said thimble into intimate contact with the inner surface of said tube, and heating to substantially the soldering temperature for said alloy, that portion of said tube in contact with said fluxcoated area of said thimble.

LEO T. MEISTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 399,879 Graydon Mar. 19, 1889 714,903 Hind Dec. 2, 1902 776,952 Skowronek Dec. 6, 1904 895,412 Badger Aug. 11, 1908 1,313,801 Doran Aug. 19, 1919 1,755,416 Wachowitz Apr. 22, 1930 1,901,469 Piccard Mar. 14, 1933 FOREIGN PATENTS Number Country Date 17,001 Great Britain Dec. 29, 1884 

